This invention relates to a mutant which mass-produces .epsilon.-poly-L-lysine (abbreviated as .epsilon.PL in the following), a method for using the mutant and a method for producing .epsilon.PL. .epsilon.PL is a high-molecular weight compound as described in the following equation in which amino groups of .epsilon.-positions of L-lysine are linked to adjacent carboxyl groups of L-lysine by amide bond formation. ##STR1##
As this material is a polymer of L-lysine which is an essential amino-acid, it has high safety and peculiar physical properties because of its high cation content. Accordingly, its utility in toiletry supplies, beauty aids, feed additives, pharmaceuticals, agricultural medicines, food additives, electronic materials, etc. is evident, give by using these properties.
Hitherto, this material was obtained by cultivating the strain of Streptomyces albulus subsp. lysinopolymerus No. 346-D (deposit No. 3834 of microorganisms of FRI) which is a .epsilon.PL production bacterium belonging to Streptomyces in a culture medium, separating it from the obtained culture materials and refining it (Japanese Patent Publication 59-20359).
However, .epsilon.PL was produced at most 0.5 g per liter of culture solution from the said strain. Accordingly, the production cost of this material was high and its wide utilization was prevented.
The inventors of the present invention have obtained a mutant mass-producing .epsilon.PL, investigated repeatedly in order to produce .epsilon.PL in large quantities by using the said mutant, and attained the following invention.